‘Fear factors’ and the price for peace of mind

Puzzled by a world in which security often trumps economics, Professor Mark Stewart is undertaking assessments of natural and man-made safety risks to prove expenditure on their reduction isn't always wise - or even necessary.

Stewart's risk-based assessments of terrorism and climate change may be textbook civil engineering, but his findings are far from what you would expect – as is his recent publishing in Playboy Magazine. Making for a prickly work environment and perhaps an even pricklier public reception, Stewart
is as unconventional as they come.

'My research can be unpopular at times,' he jokes.

'We're saying there's actually not that much to be scared about.'

While claims of these 'rather limited' safety risks could be cause for confusion in our postmillennial age of media hype and misinformation, Stewart asserts his research is all evidence-based. With more than 25 years' experience in probabilistic risk and vulnerability assessment of infrastructure and
security systems, his expertise is equally well-founded.

'Terrorism and climate change are systems, just like motor vehicles are to mechanical engineers and computers are to those in the electrical field,' he says.

'Our fundamental approach is similar too - we break down the systems to understand their different components and then integrate what we think the reduction in loss will be if you have a protective measure.'

Risky business

Stewart's risk assessments have varied applications but all intentionally pose the same question – Not are we safer, but are we spending wisely?

The multiple-award winning engineer recently sought to answer this on behalf of the US Department of Homeland Security, engaging in a joint evaluation of its expenditure with Ohio State University political scientist, John Mueller. The unorthodox duo's efforts were featured on the CNN website and in
Playboy Magazine, with their research revealing vast amounts of misspent money, as well as a gap in our theoretical understanding of current risk assessment procedures.

'Assessments nowadays seem to be a process of identifying potential sources of harm and then trying to do something about them without evaluating whether the new measures reduce risks sufficiently to justify the costs,' he explains.

Cause for pause, not alarm

One of these risks, as Stewart points out, is terrorism. It's also a risk that tends to be catastrophised in places like the United States and Australia.

'Terrorism is a low probability, high consequence event,' he declares.

'There are not that many attacks in the West and there have never been that many, especially when you compare it to the Middle East.'

'There are also more duds than successes out there.'

Stewart has received extensive Australian Research Council support over the last decade to develop probabilistic risk-modelling techniques for infrastructure subject to military and terrorist explosive blasts, as well as cost-benefit assessments of counterterrorism protection measures. Expressly influenced
by the events of 9/11, he is simultaneously looking to dispel widely held beliefs about terrorist competencies and opportunities.

'Hijacking during 9/11 was to kill people - not for cash or to peacefully negotiate the release of prisoners like it had been in the past,' he states.

'It set the benchmark for terrorism, but I think it's an outlier and not a harbinger of things to come.'

'They've since hardened cockpit doors and instructed pilots, crew and the public not to give in without a fight.'

Believing Al Qaeda 'took advantage of these vulnerabilities at the time,' Stewart largely considers the events of 9/11 as a one-off. The Director of The University's Centre for Infrastructure Performance and Reliability remains on high alert though, labelling a growing shift towards improvised explosive
devices (IEDs) as the newest hazard of terrorism. He's working with a dedicated research team to break down these individual systems, applying conventional engineering approaches and assessing their overall safety.

Funding faults

Stewart is also currently exploring cost-benefit analysis methods of police and security agencies in the United States. Set to publish his findings in a fourth book, the evidence-based engineer is again looking at what has already occurred, what is occurring, and what might occur.

'I'm asking the same questions,' he asserts.

'How many terrorist plots have there been and could there be in the future?

'How much is being spent to reduce their risk?

'Most importantly, is it worth it?

Suspecting a case of misspent money on unlikely threats akin to that of the US Department of Homeland Security, Stewart is seeking to sensibly calculate the costs of protection, as well as identify the most effective counterterrorism measures.

'We'll always compare it to 'business as usual' he says.

'To avoid overreacting, sometimes the best thing is to just accept the risk and do nothing at all.'

Mapping the winds of climate change

Stewart similarly observes a lot of worst-case thinking in the climate change arena. Also recognising the power these skewed perceptions can often hold over legislators and financial advisors, he is looking to clear up misunderstandings with the help of the CSIRO and a handful of universities.

The team's research is ongoing, and uses comparable risk assessment methods to evaluate the impact of climate change on damage and safety risks to infrastructure, as well as the cost-effectiveness of engineering adaptation strategies. Their multi-pronged approach also includes evidence-based policy
and economic theory.

'Again, we're looking at systems and threats,' Stewart says.

'But in this instance, systems are things like houses and industrial buildings, and threats are naturally-occurring, such as floods and cyclones.'

Research is currently being conducted across the country, with Stewart's collaborators at James Cook University responsible for investigating the vulnerability of houses to wind in Far North Queensland, and civil engineers at the University of New South Wales examining heat and the buckling of rail
lines. Unlike terrorism, Stewart contends protective measures for these systems don't automatically come with a hefty price tag.

'We've found you can reduce the risk of damage significantly by changing materials,' he affirms.

'It's all about detailing at a modest cost – tying the roof to the walls and the walls to the foundations.'

Mass fear and cheer

While acknowledging the pressure politicians and bureaucrats face on heated issues of climate change and terrorism, as well as the sometimes-unwise actions and expenditures that follow, Stewart is also a firm believer in practical and rational calculations.

'It's one of the reasons I like risk assessments,' he discloses.

'They're transparent so the evidence is there for people to see.'

Hoping a balance will soon be struck between cuts and pay offs, Stewart is similarly looking to standardise risk assessment procedures for a broad range of safety concerns.

'It makes sense that the public has difficulty with probabilities, especially when emotions are involved,' he remarks.

'But by giving in to fear and spending irrationally, we forgo the opportunity to use those same resources for regulations and processes that can save more lives at an equal or lower cost, such as healthcare and road safety.'

Career Summary

Biography

Mark G. Stewart is Professor of Civil Engineering and Director of the Centre for Infrastructure Performance and Reliability at The University of Newcastle in Australia. He is also currently an Australian Research Council Professorial Fellow.

He is the author, with R.E. Melchers, of Probabilistic Risk Assessment of Engineering Systems (Chapman & Hall, 1997), as well as more than 300 technical papers and reports. He has more than 25 years of experience in probabilistic risk and vulnerability assessment of infrastructure and security systems that are subject to man-made and natural hazards. Mark has received over $3 million in Australian Research Council (ARC) support in the past 10 years.

Mark has significant expertise in time and spatial dependent reliability analysis of new and existing deteriorating structures such as bridges and buildings. This has utility for assessing the safety and service-life prediction of new and existing structures. In collaboration with the CSIRO, Mark is also assessing the impact of climate change on damage and safety risks to infrastructure, and assessing the cost-effectiveness of engineering adaptation strategies. He is also a leading investigator with the reliability-based calibration of the Australian Masonry and Concrete Codes.

Since 2004, Mark has received extensive ARC support to develop probabilistic risk-modelling techniques for infrastructure subject to military and terrorist explosive blasts and cost-benefit assessments of counter-terrorism protective measures for critical infrastructure. In 2011, he received a five-year Australian Professorial Fellowship from the ARC to continue and to extend that work.

Optimisation of Blast Mitigation Strategies for Design and Strengthening of Built InfrastructureOrganisation: 1st International Conference on Analysis and Design of Structures against Explosive and Impact Loads, Tianjin
Description:

2006

Probabilistic Assessment of Corrosion Damage and Optimal Timing of Maintenance for RC StructuresOrganisation: Bridge and Infrastructure Research in Ireland
Description:

2002

Reliability and Risk Assessment of Deteriorating StructuresOrganisation: Japanese Symposium on Material and Structural Reliability, Tokyo
Description:

Reinforced concrete (RC) structures are subject to environmental actions affecting their performance, serviceability and safety. Among these actions, chloride ingress leads to corrosion initiation and its interaction with service loading could reduce its operational life. Experimental evidence indicates that chloride ingress is highly influenced by weather conditions in the surrounding environment and therefore by climate change. Consequently, both structural design and maintenance should be adapted to these new environmental conditions. This work focuses on the assessment of the costs and benefits of two climate adaptation strategies for new RC structures placed in chloride-contaminated environments under various climate change scenarios. Their cost-effectiveness is measured in terms of the benefit-to-cost ratio (BCR) and the probability that BCR exceeds unity - i.e., Pr(BCR. > 1). It was found that increasing concrete strength grade is more cost-effective than increasing design cover. The results also indicate that the cost-effectiveness of a given adaptation strategy depends mainly on the type of structural component, exposure conditions and climate change scenarios.

Mortar joint thickness has a significant effect on capacity of structural masonry. Data on mortar joint thickness (bed and head joints) were collected from twelve typical storey-h... [more]

Mortar joint thickness has a significant effect on capacity of structural masonry. Data on mortar joint thickness (bed and head joints) were collected from twelve typical storey-high walls at three different building sites and from four walls built in a research laboratory in Switzerland. The data obtained allowed an analysis of the spatial distribution of the joint thickness in each wall and the characterization of the probability distribution of joint thickness. The data has been statistically analysed and the results discussed: the central and dispersion measures were calculated and several probability distributions have been fitted to the sample data and subsequently tested using standard methods of statistical theory. Further, the results obtained from all four building sites have been compared, thus providing quantitative information about the quality of the work on different sites. The presented probabilistic information is then used to define reliability-based limit state specifications where the joint thickness acts as an important random variable. The reliability of the structural masonry subjected to a concentric normal force found that probabilistic modelling of bed joint thickness results in higher reliability indices.

Columns are the key load-bearing elements in frame structures and exterior columns are probably the most vulnerable structural components to terrorist attack. In this paper, a spa... [more]

Columns are the key load-bearing elements in frame structures and exterior columns are probably the most vulnerable structural components to terrorist attack. In this paper, a spatial reliability analysis is conducted to predict the damage for reinforced concrete (RC) columns subject to explosive blast loading. The spatial variability of material and dimensional properties of RC columns are modelled by stationary and non-stationary random fields. The variability of blast loading is also taken into consideration. Monte Carlo simulation and numerical methods are used to derive Blast Reliability Curves for RC columns under explosive loading for a number of terrorism threat scenarios, based on a high-fidelity physics-based computer programme LS-DYNA to estimate design and residual axial load-carrying capacity of RC columns. It was found that spatial variability has a significant effect on structural reliabilities and the spatial model will lead to more accurate predictions of damage and safety risks.

A changing climate and higher wind speeds means that residential construction is likely to receive more damage in the future if design standards are maintained at the current leve... [more]

A changing climate and higher wind speeds means that residential construction is likely to receive more damage in the future if design standards are maintained at the current level. The vulnerability of residential construction may be reduced by an adaptation strategy that increases design wind speeds specified by Australian standards. The paper applies break-even analysis to compare the risks, costs and benefits of climate adaptation strategies for new housing in the three largest cities in Australia: Brisbane, Sydney and Melbourne. These cities are located in southeast Australia where wind hazard is dominated by synoptic winds (thunderstorms and east-coast lows). Break-even estimates of risk reduction and adaptation cost for designing new housing to enhanced standards were calculated for three synoptic wind pattern scenarios to 2070: (1) no change, (2) B1 and (3) A1FI emission scenarios. If the actual cost of adaptation exceeds the predicted break-even value, then adaptation is not cost-effective. It was found that this adaptation strategy can lead to risk reductions of 50Â¿80Â¿% at a cost of approximately 1Â¿% of house replacement value. If risk reduction is over 50Â¿%, discount rate is 4Â¿%, and there is no change of climate, the break-even analysis shows that adaptation is cost-effective for Sydney if the adaptation cost is less than 5Â¿9Â¿% of house replacement cost. Designing new housing to enhance wind classifications is also likely to be a cost-effective adaptation strategy for Brisbane and Melbourne.

Reinforced concrete (RC) structures placed in chloride-contaminated environments are subjected to deterioration processes that affect their performance, serviceability and safety. Chloride ingress leads to corrosion initiation and its interaction with service loading could reduce its operational life. Chloride ingress and corrosion propagation are highly influenced by weather conditions in the surrounding environment including climate change. Therefore, both structural design and maintenance should be adapted to these new environmental conditions. This study focuses on the assessment of the costs and benefits of climate adaptation strategies for existing RC structures subjected to chloride ingress and climate change. We studied RC structures built at different periods under different construction standards in France. The cost-effectiveness of adaptation measures was measured in terms of the benefit-to-cost ratio (BCR) and the probability that BCR exceeds unity Â¿ i.e. Pr(BCR>1). The results of the paper could provide practical advice to policy-makers to improve the management of existing RC structures under a changing climate by discussing the influence of the following factors on the mean BCR and Pr(BCR>1): specific exposure conditions, climate change scenarios, risk reduction due to the implementation of adaptation strategies, type of structural component, years of construction and adaptation, discount rates and damage costs.

The structural integrity of reinforced concrete (RC) structures in blast events is important for critical facilities. In this paper, a structural reliability analysis is conducted... [more]

The structural integrity of reinforced concrete (RC) structures in blast events is important for critical facilities. In this paper, a structural reliability analysis is conducted to predict the damage and risk reduction for RC wall panels subjected to explosive blast loading. Due to considerable uncertainties associated with material properties, dimensions, structural response, blast loading, as well as expected damage, probabilistic methods are used in quantifying the probability of damage for conventional and blast-resistant RC precast cladding wall panels by incorporating spatial and non-spatial variables. The variability of blast loading is also taken into consideration. Monte Carlo simulation and numerical methods are utilized to predict damage of RC wall panels subject to various threat scenarios, based on a physics-based computer programme LS-DYNA to estimate maximum support rotations. It was found that spatial variability of concrete compressive strength and concrete cover has little effects on the structural reliability for precast concrete panels, and the blast-resistant wall has 5%-100% lower probability of hazardous failure than the corresponding value for a conventional wall.

In this article, we present a simple back-of-the-envelope approach for evaluating whether counterterrorism security measures reduce risk sufficiently to justify their costs. The a... [more]

In this article, we present a simple back-of-the-envelope approach for evaluating whether counterterrorism security measures reduce risk sufficiently to justify their costs. The approach uses only four variables: the consequences of a successful attack, the likelihood of a successful attack, the degree to which the security measure reduces risk, and the cost of the security measure. After measuring the cost of a counterterrorism measure, we explore a range of outcomes for the costs of terrorist attacks and a range of possible estimates for how much risk might be reduced by the measure. Then working from this mix of information and assumptions, we can calculate how many terrorist attacks (and of what size) would need to be averted to justify the cost of the counterterrorism measure in narrow cost-benefit terms. To illustrate this approach, we first apply it to the overall increases in domestic counterterrorism expenditures that have taken place since the terrorist attacks of September 11, 2001, and alternatively we apply it to just the FBI's counterterrorism efforts. We then evaluate evidence on the number and size of terrorist attacks that have actually been averted or might have been averted since 9/11.

The environment around concrete structures may be influenced by a changing climate, especially in the long run, leading to an acceleration of deterioration. Therefore, the safety,... [more]

The environment around concrete structures may be influenced by a changing climate, especially in the long run, leading to an acceleration of deterioration. Therefore, the safety, serviceability and durability of concrete infrastructure may decline at a faster rate than expected. Carbonation-induced deterioration to concrete structures constructed in Sydney, Australia and Kunming, China under a changing climate is investigated in this paper. Two emissions scenarios are considered - RCP 8.5 and RCP 4.5, representing high and medium greenhouse gas emissions scenarios respectively. The spatial time-dependent reliability analysis includes time-dependent climate scenarios and deterioration processes, as well as a large number of random variables and spatial random fields of material properties and dimensions. The surface of concrete structures is discretised into a large number of elements and the likelihood and extent of corrosion damage is calculated by tracking the evolution of the corrosion process of each element using Monte Carlo simulations. The results show that a changing climate could cause the extent of damage to increase by up to 6% for reinforced concrete infrastructure in Kunming. The findings may be used to assess climate adaptation measures in the design stage, as well as a cost-benefit analysis of climate adaptation measures.

Climate change may increase atmospheric CO2 concentration and temperature, change relative humidity (RH), and consequently change RC infrastructures' surrounding environment. Especially in the long run, the decline of the safety, serviceability and durability of RC structures may be accelerated. Carbonation induced corrosion damage of RC infrastructure in Xiamen and Shaoguan under a changing climate is investigated for time period 2010~2100. The projection of atmospheric CO2 concentration, temperature and RH in both cities are based on the representative concentration pathways (RCPs). The time-dependent reliability analysis was conducted by Monte Carlo simulation and includes the uncertainty of dimensions, material properties, climate projections, and predictive models. The corrosion damage risks of RC structures are represented by the probability of severe cracking of concrete cover. Results show that climate change may increase mean carbonation depth by 8 mm by 2100. Moreover, carbonation-induced damage risk for RC buildings in temperate areas can be increased by 12%~19%. This research provides a reference for impacts of future climate change on RC structures and development of climate adaptation strategies.

The intensity of tropical cyclones and severe storms is likely to increase due to climate change. Brisbane and the northeast coast of Queensland are regions where design wind spec... [more]

The intensity of tropical cyclones and severe storms is likely to increase due to climate change. Brisbane and the northeast coast of Queensland are regions where design wind specifications may be inadequate under either current or likely future climate conditions. An appropriate adaptation strategy may be one that increases wind classifications for new houses, which leads to a reduced vulnerability of new construction. The present paper will assess the damage risks, adaptation costs, and cost-effectiveness of these adaptation measures for residential construction in Cairns, Townsville, Rockhampton, and South East Queensland, assuming time-dependent changes in the frequency and intensity of cyclonic and noncyclonic winds to 2100. Loss functions are also developed for direct and indirect losses. It was found that increasing design wind loads for new houses in Brisbane and South East Queensland will lead to a net benefit [net present value (NPV)] of up to $10.5 billion by 2100, assuming a discount rate of 4%, which includes approximately 95% of a direct benefit and 5% of an indirect benefit. The benefits are highest for Brisbane due to its large population and the high vulnerability of existing residential construction, and have a 90-100% likelihood of achieving a net benefit by 2100.

The paper will assess terrorist threats to new and existing bridges and the cost-effectiveness of protective counter-terrorism measures. This analysis will consider threat likelih... [more]

The paper will assess terrorist threats to new and existing bridges and the cost-effectiveness of protective counter-terrorism measures. This analysis will consider threat likelihood, cost of security measures, risk reduction and expected losses to compare the costs and benefits of protective measures to bridges to decide which protective measures are cost-effective. In this paper, a break-even cost-benefit analysis determines the minimum probability of an attack, absent the protective measures, that is required for the benefit of the protective measures to equal their cost for new and existing bridges. It was found that unless terrorist threat probabilities are high, then typical protective measures are not cost-effective. Bridges and other critical infrastructure are subject to a range of natural and man-made hazards, and terrorism is most likely not as important a threat as natural hazards. It was found that economic risks to bridges from floods, earthquakes, and ship impact are higher than threats from terrorism.

This paper presents a framework to assess the potential hurricane damage risks to residential construction. Studies show that hurricane wind, frequency and/or hurricane-induced surge may change as a result of climate change; therefore, hurricane risk assessments should be capable of accounting for the impacts climate change. The framework includes a hurricane wind field model, hurricane-induced surge height model and hurricane vulnerability models. Three case study locations (Miami-Dade County, FL; New Hanover County, NC and Galveston County, TX) are presented for two types of analyses: annual regional loss estimation and event-based regional loss estimation. Demographic information, such as median house value and changes in house numbers, and distribution of houses for different exposures, is used to estimate the time-dependent probability of damage with or without possible climate change-induced change in wind speed, frequency and/or surge height. Through both analyses, it was found that climate change may have a significant impact on regional hurricane damage losses.

Netherton MD, Stewart MG, 'What are some of the problems associated with the current methods of calculating explosive blast loads?', 10th International Conference on Shock and Impact Loads on Structures 2013, 65-74 (2013)

The most common methods for calculating explosive blast loads are deterministic; in that, the output will always be the same for given model-inputs. However, a statistical analysi... [more]

The most common methods for calculating explosive blast loads are deterministic; in that, the output will always be the same for given model-inputs. However, a statistical analysis of actual explosive blast loading field (test) data reveals a high level of variability of peak reflected pressure, impulse and time of positive phase duration from repeated tests where variability would be expected to be a minimum. Given that blast-loads from similar events are highly variable, and that the most common blast-load models do not account for such circumstances, the question we should now be asking is this: How can we improve our methods for predicting blast loads, such that (known) variability and uncertainty is appropriately considered, to ensure that we continue to give useful, usable and robust information to decision makers? In other words: What exactly is the best available method for giving your Boss advice on the risks associated with explosive blast loads? This paper explores the deterministic nature of commonly used blast-load models and discusses their limitations with respect to matters such as: explosive safety distances, the design loads on protective structures and the military's deliberate use of munitions. We argue that deterministic models do not adequately account for society's usual acceptance (or rejection) of the risks associated with damage and/or injury. A new probabilistically based blast-load model is developed which does take into account the observed (and very real) variability of explosive blast loads. Following which, new forms of risk-based advice are presented. This new probabilistic blast-load model uses statistical and probabilistic information taken from the literature as well as from our own explosive trials. Explosive scenarios of future interest could be from blast-loads resulting from (possible) terrorist activity, or, from current in-service military munitions. In either case, we argue that these new forms of risk-based advice (eg: the most probable blast-load or cost-effective mitigation) provides additional - and unique - utility for decision makers involved in the production, storage and operational use of explosives. The paper concludes with a discussion on how the new probabilistic blast-loading model can improve a decision maker's confidence with respect to explosive safety distances, magazine design, protective structures design, weaponeering and collateral damage estimation.

The 'human dimension' is the unpredictable nature of human behaviour. In structural engineering tasks it can be shown that human errors result from this behaviour, for the inciden... [more]

The 'human dimension' is the unpredictable nature of human behaviour. In structural engineering tasks it can be shown that human errors result from this behaviour, for the incidence of design error is a major cause of structural failure. A Probabilistic Risk Analysis (PRA) model has been developed to simulate the effects of human error on a typical design task. The design task considered is the design of a flexural member. A computer simulation technique and event-tree methods were employed. This model provides the basis for an investigation into the efficiency of two quality management measure; namely, (i) design checking and (ii) the use of safe load tables as a design aid. Comparisons between the efficiency of design checking and the use of safe load tables will be made. It is indicated that a designer using safe load tables (or similar design aids) will be more 'cost-effective' and less prone to error than designers not using such design aids.

Reviews of statistical surveys of structural failures indicate that human error is a major cause of failure. These surveys show that human error may occur in the planning, design,... [more]

Reviews of statistical surveys of structural failures indicate that human error is a major cause of failure. These surveys show that human error may occur in the planning, design, construction, or utilisation of a structure. However, the available data suggest that design error causes a significant proportion of structural failures. An investigation of the efficiency of a quality control measure (e.g., design checking) is reported which includes design checking guidelines for the structural engineering profession. The use of safe load tables (for steel member design) as a quality assurance measure is also investigated. It is indicated that a designer using safe load tables (or similar design aids) will be more 'cost effective' and less prone to error than designers not using such design aids. Comparisons between the efficiency of design checking and the use of safe load tables will be made.

On 28 December, 1989 the city of Newcastle was struck by a magnitude 5.6 earthquake killing 12 people and causing losses estimated at $1000 million. It was the first time a major ... [more]

On 28 December, 1989 the city of Newcastle was struck by a magnitude 5.6 earthquake killing 12 people and causing losses estimated at $1000 million. It was the first time a major Australian city has been so extensively damaged as a result of an earthquake, and the first time that deaths have occurred. With a few exceptions, most of the damage was to older loadbearing masonry construction or to infill masonry in modern framed construction. There was relatively little structural damage to modern buildings, industrial facilities and lifelines. This paper reviews the damage to structures and brings out the main points to be considered in future design and construction.

The process of structural design has received very little attention from the research community despite its centralness in day-to-day structural engineering. Much of the research ... [more]

The process of structural design has received very little attention from the research community despite its centralness in day-to-day structural engineering. Much of the research which has been done has been carried out in Australia over a number of years and with the co-operation of many structural engineers. The present paper reviews the reasons for being engaged in this relatively unusual research activity and provides an overview of the work to date. A review is given of the incidence and type of errors made in basic design tasks such as calculations, table look-up and table interpolation, and how these errors relate to results obtained for more comprehensive tasks such as loading determination and member design. One of the outcomes of the work has been to suggest areas in certain current design codes which are prone to misinterpretation by practitioners. Preliminary results related to design computation checking and inspection are also reviewed. This work potentially has major implications for quality assurance programmes.

Peng L, Stewart MG, 'Corrosion and damage risks for reinforced concrete infrastructure in China due to a changing climate', Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures - Proceedings of the 11th International Conference on Structural Safety and Reliability, ICOSSAR 2013, New York, US (2014) [E1]

Modelling of structural damage caused by explosive blast loads first requires knowledge of the characteristics of the blast load. Most vulnerability assessments assume that an IED... [more]

Modelling of structural damage caused by explosive blast loads first requires knowledge of the characteristics of the blast load. Most vulnerability assessments assume that an IED will reach maximum TNT equivalency, and that the IED will successfully detonate. These assumptions will tend to over-estimate actual blast load effects. The paper develops an IED Probabilistic Risk Assessment model using a systems model for IED attacks based on IED device reliability and characterising the human aspects of IED attack operational effectiveness from existing databases of terrorist incidents. It was found that it the risk of loss (fatalities, property damage) is influenced more by the operational aspects of an attack (such as target selection, IED placement and attack timing) than the technical aspects of the device (i.e., design and manufacture).

2013

Stewart MG, Mueller J, 'Terror, security, and money: The risks, benefits, and costs of critical infrastructure protection', From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012, Sydney (2013) [E1]

Reinforced concrete (RC) structures deteriorate with time and corrosion of reinforcing steel is one of the main causes for that. In the paper a framework for reliability-based ass... [more]

Reinforced concrete (RC) structures deteriorate with time and corrosion of reinforcing steel is one of the main causes for that. In the paper a framework for reliability-based assessment of durability of RC concrete structures in corrosive environments will be briefly described. Existing models for corrosion initiation, corrosion-induced cracking, and effects of corrosion on stiffness and strength of RC members will be considered. Special attention will be paid to the effects of a changing climate on corrosion risks to RC structures.

Stewart MG, Mullard JA, 'Reliability based assessment of the influence of concrete durability on the timing of repair for RC bridges', Proceedings of the Third International Conference on Bridge Maintenance, Safety and Management - Bridge Maintenance, Safety, Management, Life-Cycle Performance and Cost, Porto, Portugal (2006) [E2]

Stewart MG, Darmawan MS, 'Structural Performance, Reliability And Service Life Prediction Of Concrete Beams Subject To Pitting Corrosion', Proceedings of the Second International Conference on Structural Engineering, Mechanics and Computation, Capetown, South Africa (2004) [E1]

2004

Maes MA, Stewart MG, 'Optimizing Structural Safety Levels On The Basis Of Lifetime Utility Objectives Of The Individual', Proceedings of the Second International Conference on Structural Engineering, Mechanics and Computation, Capetown, South Africa (2004) [E1]

2004

Stewart MG, Vu KAT, 'Predicting The Proportion Of A Concrete Surface Subject To Corrosion-Induced Cracking And Damage', Proceedings of the Second International Conference On Bridge Maintenance, Safety and Management, Kyoto, Japan (2004) [E2]

Darmawan MS, Stewart MG, 'Spatial Variability Of Pitting Corrosion And Its Effect On The Reliability Of Prestressing Wires', Proceedings of the 9th International Conference On Applications Of Statistics And Probability In Civil Engineering, San Francisco, California (2003) [E1]

Citations

Web of Science - 2

2003

Val DV, Stewart MG, 'Life-Cycle Cost Analysis As A Tool For Decision Making', Proceedings of the 9th International Conference On Applications Of Statistics And Probability In Civil Engineering, San Francisco, California (2003) [E1]

2003

Stewart MG, Faber MH, 'Probabilistic Modelling Of Deterioration Mechanisms For Concrete Structures', Proceedings of the 9th International Conference On Applications Of Statistics And Probability In Civil Engineering, San Francisco, California (2003) [E1]

Investigating the Correlation Between Pre- and Post-Demolition Assessments for Precast, Post-Tensioned Beams in Service for 45 YearsCivil Engineering, Faculty of Engineering and Built EnvironmentCo-Supervisor

2009

Pollution Deposition Rates on Insulator (HV) Surfaces for Use in Atmospheric Corrosivity EstimationCivil Engineering, Faculty of Engineering and Built EnvironmentCo-Supervisor

2007

An Investigation Into Structural FailureCivil Engineering, Faculty of Engineering and Built EnvironmentCo-Supervisor